My parents' kitchen could be mistaken for the vitamin and supplement aisle at Target. They have everything from vitamin D3 and B-complex 100 to milk thistle and magnesium. There are things I’ve never heard about, like echinacea, and things I’m not entirely sure need to come in supplement form, like cinnamon. I could go on.

So naturally I could relate when, in a recent interview with Harper's Bazaar, Jennifer Aniston said she takes a lot of vitamins, and that her choices change all the time. She mentioned how once someone points out that you don’t take something—“‘Oh my god, you don’t take activated charcoal?’”—you begin going down the “Google hole” to understand the benefits of whatever it is you apparently should be benefitting from.

I’ve definitely been down that hole (and I’m guessing you have, too), and not just because of my parents—while they’re asking me to Google X, Y, and Z they heard on Dr. Oz that afternoon, I’ve got my own tabs open. Should I really pick up those Sugar Bear hair vitamins just because Vanessa Hudgens looked really pretty advertising them on Instagram? Even trend skeptics can be intrigued or even tempted to try the latest craze—provided it’s not too out there.

But the truth is, in general, most people don’t really need vitamins or supplements. (For more, read SELF’s recent report Is Taking Vitamins Ever Useful?) Here are a few ways to decide if whatever vitamin is currently trending is actually right for you:

If you have to sneak into your savings for a quick vitamin splurge, don’t.

Most vitamins are a waste of money. According to the National Center for Health Statistics, Americans spend $30.2 billion a year on vitamins that might not be doing anything for them. In a 2013 study published in the Annals of Internal Medicine, the authors concluded that there is no clear evidence that supplements have any effect on life span or preventing cancer and cardiovascular diseases.

“A lot of products on the market are safe, but it’s just trying to understand what your body chemistry needs, otherwise you’re giving it almost more of a burden than it would really need,” Taz Bhatia, M.D., integrative health expert and author of Super Woman RX, tells SELF. One reason is because some vitamins don’t even have the same ingredients they claim to on the bottle—the New York State attorney general’s office conducted a study in 2015 and found that certain supplements “included filler ingredients like rice, beans, pine, citrus, asparagus, wheat, and wild carrots” instead of the herbs they were supposed to.

You should only take supplements once your doctor has determined that you have a specific deficiency.

Don’t self-diagnose and start an activated charcoal cleanse because you’ve been extra gassy for a few days. But, it is OK to ask for certain blood tests if you're experiencing symptoms or concerned about a certain deficiency. Dr. Bhatia recommends going to your doc prepared with a checklist of three or four things that are signs you might have deficiencies—which means anything having to do with your energy, the condition of your hair and skin, and if you’re experiencing any pain. Docs might not include things like vitamin D and omega-3 in standard blood tests, so mention that you're interested in being tested for deficiencies if you’re concerned (and know that the tests may cost extra money depending on your insurance). Keep in mind that low levels of a certain vitamin don't necessarily mean that you need supplements. Talk with your doctor about your results and your treatment plan.

There are some groups who are particularly susceptible to deficiencies and should ask their doctor about tests.

If you’re a woman who has heavy periods, you might need an iron supplement. Vegans and vegetarians might benefit from B12, which is found in eggs and milk. “When you have a B12 deficiency, it can cause neurologic problems, so you definitely need to account for it,” endocrinologist Sheela Magge previously told SELF. Your period or diet isn’t the only reason you might need to get some blood drawn: people who are very pale and live in northern climates could be lacking vitamin D.

If you do happen to fit in any of these categories, make sure you have that talk with your doc—it is totally possibly to get too high of a dose of certain supplements, especially on ones like iron, which can easily accumulate in your body. “The biggest issue in practice is over-supplementation,” says Dr. Bhatia. “It’s hard on the digestion system, and in turn there’s no way [your gut] can absorb that much stuff, so it may not even be doing anything at the end of the day.”

Once you’ve determined that you have a deficiency, work with your doctor to know when you should taper down the vitamin or stop taking it.

Basically, don’t be Aniston—at least when it comes to this. (Copying her in pretty much any other area of life: totally approved.) “Jennifer is just like everybody else—everyone is trying to optimize themselves,” says Dr. Bhatia. “And that’s where I strongly encourage folks to sit with someone who can help them navigate that conversation.”